Folding propeller



March 14, 1950 E.H. ROWLEY 2,500,382

FOLDING PROPELLER Filed July 20, 1945 2 Sheets-Sheet l ELTON H. ROWLEY INVENTOR ATTORNEY March 14, 1950 ROWLEY 2,500,382

FOLDING PROPELLER Filed July 20, 1945 I 2 Sheets-Sheet 2 FIG. 4

llllllllllllllll L ELTON H. ROWLEY FIG. 3 INVENTOR ATTORNEY Patented Mar. 14, 1950 UNITED STATES PATENT assess;

OFFICE FOLDING PROPELLER Elton H. Rowley, Wichita, Kans.

Application July 20, 1945, Serial No. 606,174

Claims. (Cl. 170-46012) This invention relates to folding propellers for aircraft, more particularly for powered gliders.

It is the chief object of the invention to provide a propeller, the blades of which automatically fold to a low drag position as soon as the engine is stopped, thus decreasing drag far below that of a feathered conventional propeller.

It is a further object of the invention to provide a propeller in which the folding blades are interconnected to assure their proportionate movement toward either the folded or unfolded position, thus maintaining proper balance and eliminating excess vibration during folding or unfolding of the blades.

Another object is to provide a propeller of this type in which the folding and unfolding of the blades is under the direct control of a dash pot which prevents snap opening of the blades when the engine is started, and snap closing as the propeller rotational speed reduces toward zero.

Briefly, a propeller embodying the invention includes a pair of blades having their roots connected to opposite sides of the propeller hub by parallel transversely disposed pivotal axes lying outside and normal to the rotational axis of the propeller; a pair of rack 'bars slidably mounted on opposite sides of the hub adjacent the blade roots; sector type pinions secured to and movable with the blade roots, and adapted to mesh with the rack bars and to force the bars to move in unison along a path parallel to the propeller rotational axis; a cross arm rigidly connecting the outer ends of the rack bars, and itself connected to a plunger rod which extends into .an oil filled dash pot located centrally in the propeller hub; a coil spring inside the dash pot urging the plunger rod and consequently the rack bars in a direction to move the blades toward a folded position i. e.a position parallel to each other and to the rotational axis of the propeller.

The details in the construction of one preferred embodiment of the invention together with other objects attending its use will be better understood after the following detailed description is read in connection with the accompanying drawings, which are presented for illustrative purposes only and which are not to be construed as limiting the scope of the invention.

In the drawings:

Figure 1 is a side elevation of a propeller hub assembly embodying the invention, only fragments of the blades being shown;

Figure 2 is a front elevation of the same assembly;

sockets i6 and I7, and these sockets are pivotally connected on opposite sides of the hub by means of bolts l8 and IS, a suitable connection being clearly shown in Figures 2 and 4. From Figure l it will be clearly seen that the bolts l8 and H! are splined intermediate their ends for non rotatable fit in the inner ends of the sockets l6 and M respectively. These bolts turn freely within sleeve bearings mounted in the journal ears 20, 2!, 22, and 23. Near its opposite ends the bolt I3 carries sector type pinions 24 and 25 which have a splined connection with the bolt. Spacers 26 and 21, washers 28 and 29, and nuts 30 complete the blade mounting. Similarly the bolt 59 carries sector type pinions 32 and 33, which are spaced from the adjacent cars by means of spacers 34 and 35, and are held in position on the bolt by washers 36 and 31, and nuts 38. It will be seen that the bolts 33 and 19 are parallel to each other on opposite sides of the hub, are transversely disposed, and lie in a position normal to the rotational axis of the hub. Thus when the blades fold to the dotted line position in Figure 1, they assume positions parallel to each other and parallel to the rotational axis of the propeller.

A pair of rack bars 40 and M are slidably mounted at opposite sides of the hub It for movement in parallel planes which are also parallel to the axis of the rotation of the hub H1. The movement of these rack bars is guided by guides 62 and 43 which are respectively provided with removable flanges 44 and 45, and 26 and Lil, held in position by suitable stud bolts 48.

The outer toothed edges of the rack bars mesh with the adjacent pinions 24, 25, 32, and 33, on opposite sides of the hub. The outer ends of the rack bars are rigidly secured together by means 01' a cross arm 49, theconnection being made by stud bolts and El. Centrally the cross arm G5 is secured to the outer end of a plunger rod 52 by means of a nut 53.

Referring more particularly to Figure 3, it will be seen that the hub I0 is centrally bored to form a cylinder, open at the outer end. A suitable liner 5 is provided for this cylinder, and the inner end of the plunger rod extends into the cylinder and carries a plunger 55 which is provided with a bleed hole 56, the plunger being mounted in any suitable manner. The plunger rod 5'2 reciprocates through a packing gland 51 mounted in a closure or a cap 58. A coiled spring 59 is mounted within the cylinder surrounding the plunger rod, one end of the spring bearing against the plunger, and the opposite end bearing against the closure 2-58, and being centered thereby. The spring 59 normally maintains the plunger at the left hand end of the cylinder in Figure 3. This means that the rack bars 48 and M are also normally maintained at the left hand end of their respective paths of travel, as shown by the dotted lines in Figure l. The movement of the rack bars to this position naturally forces the blade sockets l6 and H into the dotted line positions, whereby the drag of the entire propeller is greatly reduced.

Movement of the blades in opposite directions is limited by the contact of the surfaces Gil, 5i, 852, and 53 of the rack bars with the adjacent edges of the guides 32 and 53. Movement of the blades into a position normal to the rotational axis of the propeller is also limited by contact of a portion of the hubs HS and ii with integral upstanding collars 54 and 65 carried by the propeller hub, as clearly shown in Figure 1.

With the propeller at rest, the blades will re main in the dotted line positions of Figure 1. When the engine is started and the propeller begins to rotate, centrifugal force causes the blades to move toward the solid line positions of Figure 1, simultaneously rotating the pinions 2G, 25, 32, and The pinions force the rack bars to their solid line positions in Figure 1, and in doing so force the piston 55 to travel toward the cap 58 against the action of the spring 53, and also against the damping action of the oil trapped in that end of the cylinder 5t. During this movement, oil flows through the bleed hole 55 to the opposite side of the piston, and the fluid flow area of the bleed hole determines the speed at which the piston 55 is permitted to travel, in a manner which is common and well known. So long as the propeller shaft H continues to be driven by the engine, the propeller blades M and i5 remain in their operative positions. In use on a motor powered glider, when suificient altitude has been attained, the pilot cuts oiT the motor. As soon as the propeller speed reduces, the accompanying reduction in centrifugal force permits the spring 59 through its action on the rack bars and pinions to return the blades to their normal inoperative positions parallel to the propeller axis.

From this description it will be seen that I have provided a folding propeller of rugged but simple construction-one which produces a result which has not, to my knowledge, been produced by presentl known types of propellers.

While only a single embodiment of the invention has been described, it is to be understood that the described details are not intended to limit the invention except as they define the terms in the appended claims.

- I claim:

1. A folding propeller assembly comprising: a hub adapted for attachment to a driving shaft; a pair of blades having their roots pivotally mounted on opposite sides of said hub on parallel. axes which are transverse to the hub rotational axis; a pair of rack bars mounted on opposite sides of the hub between the blades for slidable axial travel with relation to the hub; gear sectors mounted on the respective blade roots at their pivotal axes and meshed with said rack bars; a cross arm rigidly connecting two adjacent ends of said rack bars; a dash pot assembly within the bub including a cylinder, a piston, and a piston rod, the exterior end of the piston rod being rigidly connected to said cross arm, whereby said dash pot damps the movement of said rack bars, and consequently of said blades, in both direc tions; and spring means urging the piston rod and the rack bars in a direction to force the blades toward a folded position.

2. A folding propeller assembly comprising: a hub adapted for attachment to a driving shaft; a pair of blades having their roots pivotally mounted on opposite sides of said hub on parallel axes which are transverse to the hub rotational axis; a pair of rack bars mounted on opposite sides of the hub between the blades for slidable axial travel with relation to the hub; gear sectors mounted on the respective blade roots at their pivotal axes and meshed with said rack bars; a cross arm rigidly connecting two adjacent ends of said rack bars; a dash pot assembly within the hub including a cylinder, a piston, and a piston rod, the exterior end of the piston rod being rigidly connected to said cross arm, whereby said dash pot damps the movement of said rack bars, and consequently of said blades, in both directions; spring means urging the piston rod and the rack bars in a direction to force the blades toward a folded position; and means limiting the movement of the rack bars, and consequently of the propeller blades, in both directions.

3. A folding propeller assembly comprising: a hub adapted for attachment to a driving shaft; opposed blade root sockets on the hub, each socket having a portion of its wall cut away; a pair of blades having their respective roots pivotally mounted in said sockets on parallel axes which are transverse to the hub rotational axis: a pair of rack bars slidably mounted on opposite sides of the hub between'the blade pivot axes; gear sectors mounted on the respective blade roots at their pivot axes and meshed with said rack bars; a cross arm rigidly connecting two ad a-cent ends of said rack bars; and a dash pot assembly housed within the hub including a cylinder. a piston, and a piston rod, the exterior end of the piston rod being rigidly connected to said cross arm. whereby said dash pot damps the movement of said rack bars, and conseouentlv of said blades, in both directions around the blade pivot axes.

4. A folding propeller assembly com rising: a hub adapted for attachment to a drivin shaft; opposed blade root sockets on the hub, each socket having a portion of its wall cut away: a pair of blades having their respective roots pivotally mounted in said sockets on parallel axes which are transverse to the hub rotational axis; a pair of rack bars slidably mounted on opposite sides of the hub between the blade pivot axes; gear sectors mounted on the respective blade roots at their pivot axes and meshed with said rack bars; a cross arm rigidly connecting two adjacent ends of said rack bars: a dash pot assembly housed within the hub including a cylinder, a piston, and a piston rod, the exterior end of the piston rod being rigidly connected to said cross arm, whereby said dash pot damos the movement of said rack bars, and consequently of said blades, in both directions around the blade pivot axes; and spring means urging the piston rod and consequently the rack bars in a direction to force the blades to pivot toward a folded position substantially parallel to the hub rotational axis.

5. A folding propeller assembly comprising: a hub adapted for attachment to a driving shaft; opposed blade root sockets on the hub, each socket having a portion of its Twall cut away; a pair of blades having their respective roots pivotally mounted in said sockets on parallel axes which are transverse to the hub rotational axis; a pair of rack bars slidably mounted on opposite sides of the hub between the blade pivot axes; gear sectors mounted on the respective blade roots at their pivot axes and meshed with said rack bars; a cross arm rigidly connecting two adjacent ends of said rack bars; a dash pot assembly housed within the hub including a; cylinder, a piston, and a piston rod, the exteriorend of the piston rod being rigidly connectedfto'said cross arm, whereby said dash pot dampsjthe movement of said rack bars, and consequently of said blades, in 20 both directions around the blade pivot axes; spring means urging the piston rod and conse- REFERENCES CITED The following references are of record in the f this patent:

UNITED STATES PATENTS Name Date Dorner Apr. 23, 1940 FOREIGN PATENTS N ber Country Date 22,189 Great Britain of 1895 60,488 Norway Dec. 4, 1939 323,641 Germany Aug. 3, 1920 411,631 Germany Mar. 28, 1925 

